Overlay mark dependent dummy fill to mitigate gate height variation

ABSTRACT

A method of forming dummy structures and an overlay mark protection zone over an active layer zone based on the shape of an overlay mark and the resulting device are provided. Embodiments include determining a size and a shape of an overlay mark; determining a size and a shape of an overlay mark protection zone based on the shape of the overlay mark; determining a shape of a plurality of dummy structures based on the shape of the overlay mark; determining a size and a shape of an active layer zone based on the size and the shape of the overlay mark and the plurality of dummy structures; forming the active layer zone in an active layer of a semiconductor substrate; forming the overlay mark and the plurality of dummy structures over the active layer zone in a poly layer of the semiconductor substrate; and planarizing the poly layer.

TECHNICAL FIELD

The present disclosure relates to semiconductor device overlaymeasurement processes. The present disclosure is particularly applicableto semiconductor overlay mark alignment processes for 20 nanometer (nm)technology nodes and beyond.

BACKGROUND

Current overlay measurements are often not stable due to gate heightvariation within the polysilicon (poly) layer, which results fromchemical mechanical polishing (CMP) of the poly layer. As a result ofthe over polishing, for example, the requisite contrast between layersis degraded, which produces overlay metrology noise and preventsaccurate gate to trench block (TB) overlay data feedback to a scannerfor correction.

A need therefore exists for methodology enabling reduced gate heightvariation of a poly layer after CMP for stable overlay measurements, andthe resulting device.

SUMMARY

An aspect of the present disclosure is method of forming a plurality ofdummy structures and an overlay mark protection zone over at least oneactive layer zone based on the shape of an overlay mark.

Another aspect of the present disclosure is a device including aplurality of dummy structures formed in a poly layer over an activelayer zone based on the shape of the overlay mark.

Additional aspects and other features of the present disclosure will beset forth in the description which follows and in part will be apparentto those having ordinary skill in the art upon examination of thefollowing or may be learned from the practice of the present disclosure.The advantages of the present disclosure may be realized and obtained asparticularly pointed out in the appended claims.

According to the present disclosure, some technical effects may beachieved in part by a method including: determining a size and a shapeof an overlay mark; determining a size and a shape of an overlay markprotection zone based on the shape of the overlay mark; determining ashape of a plurality of dummy structures based on the shape of theoverlay mark; determining a size and a shape of at least one activelayer zone based on the size and the shape of the overlay mark and theplurality of dummy structures; forming the at least one active layerzone in an active layer of a semiconductor substrate; forming theoverlay mark and the plurality of dummy structures over the at least oneactive layer zone in a poly layer of the semiconductor substrate; andplanarizing the poly layer.

Aspects of the present disclosure include forming the plurality of dummystructures in four distinct dummy fields; forming the overlay markprotection zone in a square or rectangle shape; and aligning eachdistinct dummy field adjacent to a different corner of the overlay markprotection zone. Other aspects include forming the overlay mark in asquare or a rectangle shape; forming the overlay mark protection zone ina square or a rectangle shape, respectively, with a width outside of theoverlay mark greater than zero; and forming the plurality of dummystructures in four distinct dummy fields each having a square or arectangle shape, respectively. Further aspects include forming theoverlay mark in a cross shape; and forming the overlay mark protectionzone in a square or a rectangle equal to or larger than a smallestsquare that can be formed around the overlay mark. Another aspectincludes forming the plurality of dummy structures in four distinctdummy fields; and forming each of the four distinct dummy fields in asquare, a rectangle, or a right angle shape. Additional aspects includeforming the at least one active layer zone in a cross shape; and formingeach of the four distinct dummy fields in the right angle shape. Otheraspects include forming the at least one active layer zone in a squareor rectangle shape; and forming each of the four distinct dummy fieldsin the square or the rectangle shape, respectively. Further aspectsinclude forming the at least one active layer zone as fivenon-contiguous regions based on the size, the shape, and respectivelocations of the overlay mark and the plurality of dummy structures.Another aspect includes planarizing the poly layer by CMP.

Another aspect of the present disclosure is a device including: asemiconductor substrate; an active layer including at least one activelayer zone; and a poly layer over the active layer and including anoverlay mark and a plurality of dummy structures, each formed on the atleast one active layer zone. Aspects of the device include a size and ashape of the at least one active layer zone being determined based on asize, a shape and a location of the overlay mark and the plurality ofdummy structures. Other aspects include the plurality of dummystructures being formed in four distinct dummy fields. Further aspectsinclude a square or rectangular overlay mark protection zone beingformed around the overlay mark, wherein each of the four distinct dummyfields is formed adjacent to a different corner of the overlay markprotection zone. Another aspect includes the overlay mark being formedin a square or a rectangle, an overlay mark protection zone being formedin a square or rectangle shape, respectively, with a width outside ofthe overlay mark being greater than zero, and each of the plurality ofdummy structures being formed in a square or a rectangle shape,respectively. Additional aspects include the overlay mark being formedin a cross and the at least one active layer being is formed in a squareor rectangle shape, an overlay mark protection zone being formed in asquare or a rectangle equal to or larger than a smallest square that canbe formed around the overlay mark, and each of the plurality of dummystructures being formed in a square or a rectangle shape. Other aspectsinclude the overlay mark being formed in a cross and the at least oneactive layer being formed in a cross shape, an overlay mark protectionzone being formed in a square shape equal to or larger than a smallestsquare that can be formed around the overlay mark, and each of theplurality of dummy structures being formed in a right-angle shape.

Another aspect of the present disclosure is a method including:determining a size and a shape of an overlay mark; determining a sizeand a shape of an overlay mark protection zone around the overlay markbased on the shape of the overlay mark; determining a shape of aplurality of dummy structures based on the shape of the overlay mark;determining a size, a shape and a location of at least one active layerzone based on the size, the shape and a location of the overlay mark andthe plurality of dummy structures; forming the at least one active layerzone in an active layer of a semiconductor substrate; forming theoverlay mark over the at least one active layer zone in a poly layer ofthe semiconductor substrate; forming the plurality of dummy structuresin four distinct dummy fields in the poly layer, outside, but adjacentto, the overlay mark protection zone, each dummy field based on theshape of the overlay mark; and planarizing the poly layer by CMP. Otheraspects include forming the overlay mark in a square or a rectangleshape; forming the overlay mark protection zone in a square or arectangle shape, respectively, with a width outside of the overlay markgreater than zero; and forming each of the four distinct dummy fields ina square or a rectangle shape, respectively, diagonally aligned with adifferent corner of the overlay mark protection zone. Further aspectsinclude forming the overlay mark in a cross shape; and forming theoverlay mark protection zone in a square or a rectangle shape equal toor greater than a smallest square that can be formed around the overlaymark; and forming the active layer zone in a square or rectangle shapeand forming each of the four distinct dummy fields in a square or arectangle shape, respectively, diagonally aligned with a differentcorner of the overlay mark protection zone, or forming the active layerzone in a cross shape and forming the overlay protection zone in asquare and each of the four distinct dummy fields in a right-angle shapeat a different corner of the overlay mark protection zone. Anotheraspect includes forming the least one active layer zone as fivenon-contiguous regions.

Additional aspects and technical effects of the present disclosure willbecome readily apparent to those skilled in the art from the followingdetailed description wherein embodiments of the present disclosure aredescribed simply by way of illustration of the best mode contemplated tocarry out the present disclosure. As will be realized, the presentdisclosure is capable of other and different embodiments, and itsseveral details are capable of modifications in various obviousrespects, all without departing from the present disclosure.Accordingly, the drawings and description are to be regarded asillustrative in nature, and not as restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is illustrated by way of example, and not by wayof limitation, in the figures of the accompanying drawing and in whichlike reference numerals refer to similar elements and in which:

FIGS. 1A and 1B schematically illustrate forming a plurality of dummystructures and an overlay mark protection zone over an active layer zonebased on an overlay mark formed in a square or a rectangle shape, inaccordance with an exemplary embodiment;

FIGS. 2A and 2B schematically illustrate forming a plurality of dummystructures and an overlay mark protection zone over an active layer zonebased on an overlay mark formed in a cross shape, in accordance with anexemplary embodiment;

FIG. 3 schematically illustrates forming a plurality of L-shaped dummystructures and an overlay mark protection zone over an active layer zonebased on an overlay mark formed in a cross shape, in accordance with anexemplary embodiment; and

FIG. 4 schematically illustrates forming a plurality of dummy structuresand an overlay mark protection zone over a plurality of active layerzones based on an overlay mark formed in a cross shape, in accordancewith an exemplary embodiment.

DETAILED DESCRIPTION

In the following description, for the purposes of explanation, numerousspecific details are set forth in order to provide a thoroughunderstanding of exemplary embodiments. It should be apparent, however,that exemplary embodiments may be practiced without these specificdetails or with an equivalent arrangement. In other instances,well-known structures and devices are shown in block diagram form inorder to avoid unnecessarily obscuring exemplary embodiments. Inaddition, unless otherwise indicated, all numbers expressing quantities,ratios, and numerical properties of ingredients, reaction conditions,and so forth used in the specification and claims are to be understoodas being modified in all instances by the term “about.”

The present disclosure addresses and solves the current problem ofunstable overlay measurements attendant upon gate height variation in apoly layer after CMP. By forming both the overlay mark and the dummystructures on an active layer zone, gate height variation can be reducedand overlay stability improved.

Methodology in accordance with embodiments of the present disclosureincludes determining a size and a shape of an overlay mark. A size and ashape of an overlay mark protection zone are determined based on theshape of the overlay mark. A shape of a plurality of dummy structures isdetermined based on the shape of the overlay mark. A size and a shape ofat least one active layer zone are determined based on the size and theshape of the overlay mark and the plurality of dummy structures. The atleast one active layer zone is formed in an active layer of asemiconductor substrate. The overlay mark and the plurality of dummystructures are formed in a poly layer of the semiconductor substrateover the at least one active layer zone. The poly layer is planarized.

Still other aspects, features, and technical effects will be readilyapparent to those skilled in this art from the following detaileddescription, wherein preferred embodiments are shown and described,simply by way of illustration of the best mode contemplated. Thedisclosure is capable of other and different embodiments, and itsseveral details are capable of modifications in various obviousrespects. Accordingly, the drawings and description are to be regardedas illustrative in nature, and not as restrictive.

Adverting to FIG. 1A, once a size and a shape of an overlay mark 101 aredetermined, e.g., a square, the size and the shape of an overlay markprotection zone 103 are determined based on the shape of the overlaymark 101. In particular, if the shape of the overlay mark 101 is asquare, then the overlay mark protection zone 103 is also formed in asquare shape with a width outside of the overlay mark 101 greater thanzero. Next, the shape of a plurality of dummy structures 105, e.g., asquare, is determined based on the shape of the overlay mark 101. A sizeand a shape of an active layer zone 107, e.g., a square, are thendetermined based on the size and shape of the combination of the overlaymark 101 and the plurality of dummy structures 105. Thereafter, theactive layer zone 107 is formed in an active layer of a semiconductorsubstrate (not shown for illustrative convenience). The overlay mark 101and the plurality of dummy structures 105 are then formed over theactive layer zone 107 in a poly layer of the semiconductor substrate(not shown for illustrative convenience). In particular, the pluralityof dummy structures 105 are formed in four distinct dummy fields andeach distinct dummy field is aligned adjacent to a different corner ofthe overlay mark protection zone 103. Thereafter, the poly layer isplanarized by CMP.

In FIG. 1B, similar to FIG. 1A, once a size and a shape of an overlaymark 101′ are determined, e.g., a rectangle in this case, the size andthe shape of an overlay mark protection zone 103′, e.g., a rectangle,are determined based on the shape of the overlay mark 101′. Also similarto FIG. 1A, if the shape of the overlay mark 101′ is a rectangle shape,then the overlay mark protection zone 103′ is formed in a rectangleshape with a width outside of the overlay mark 101′ greater than zero.Next, the shape of a plurality of dummy structures 105′, e.g., arectangle, is determined based on the shape of the overlay mark 101′. Asize and a shape of an active layer zone 107′, e.g., a rectangle, arethen determined based on the size and the shape of the overlay mark 101′and the plurality of dummy structures 105′. Thereafter, the active layerzone 107′ is formed in an active layer of a semiconductor substrate (notshown for illustrative convenience). The overlay mark 101′ and theplurality of dummy structures 105′ are then formed over the active layerzone 107′ in a poly layer of the semiconductor substrate (not shown forillustrative convenience). As in FIG. 1A, the plurality of dummystructures 105′ are formed in four distinct dummy fields and eachdistinct dummy field is aligned adjacent to a different corner of theoverlay mark protection zone 103′. Thereafter, the poly layer isplanarized by CMP.

The processes of FIGS. 2A and 2B are nearly identical to the processesof FIGS. 1A and 1B, respectively, except that the overlay marks 201 and201′ are cross-shaped instead of the square overlay mark 101 and therectangle overlay mark 101′. If the shape of the overlay mark 201 is across shape and the plurality of dummy structures 205 are formed in asquare shape, then the overlay mark protection zone 203 is formed in asquare shape equal to or larger than the smallest square that can beformed around the overlay mark 201, as illustrated in FIG. 2A.

However, if the shape of the overlay mark 201′ is a cross shape and theplurality of dummy structures 205′ are formed in a rectangle shape, thenthe overlay mark protection zone 203′ is formed in a rectangle shapeequal to or larger than the smallest rectangle that can be formed aroundthe overlay mark 201′.

Adverting to FIG. 3, similar to FIGS. 2A and 2B, once a size and a shapeof an overlay mark 301 are determined, e.g., a cross shape, the size andthe shape of an overlay mark protection zone 303 are determined based onthe shape of the overlay mark 301. Since the shape of the overlay mark301 is a cross shape, then the overlay mark protection zone 303 may beformed in a square or a rectangle shape equal to or larger than thesmallest square or rectangle, respectively, that can be formed aroundthe overlay mark 301. Next, the shape of a plurality of dummy structures305, e.g., an L-shape, is determined based on the shape of the overlaymark 301. A size and a shape of an active layer zone 307, e.g., a crossshape, are then determined based on the size and shape of the overlaymark 301 and the plurality of dummy structures 305. Thereafter, theactive layer zone 307 is formed in an active layer of a semiconductorsubstrate (not shown for illustrative convenience). The overlay mark 301and the plurality of dummy structures 305 are then formed over theactive layer zone 307 in a poly layer of the semiconductor substrate(not shown for illustrative convenience). In particular, the pluralityof dummy structures 305 are formed in four distinct dummy fields, eachin a right-angle shape at a different corner of the overlay markprotection zone 303. Thereafter, the poly layer is planarized by CMP.

The overlay mark protection zone may alternatively be determined to bemuch greater than the smallest square that can be formed around theoverlay mark, as depicted in FIG. 4. Similar to FIG. 2A, once a size anda shape of an overlay mark 401 are determined, e.g., a cross shape, thesize and the shape of an overlay mark protection zone 403 are determinedbased on the shape of the overlay mark 401. Next, the shape of aplurality of dummy structures 405, e.g., a square shape, is determinedbased on the shape of the overlay mark 401. A size and a shape of theactive layer zone 407, are then determined based on the size and shapeof the overlay mark 401 and the plurality of dummy structures 405.However, rather than having one large active layer zone that can supportthe protection zone and all four dummy structures, the active layer zone407 is formed as five non-contiguous regions based on the size, theshape, and respective locations of the overlay mark 401 and theplurality of dummy structures 405. Thereafter, the five non-contiguousactive layer zones 407 are formed in an active layer of a semiconductorsubstrate (not shown for illustrative convenience). The overlay mark 401and the plurality of dummy structures 405 are then formed over the fivenon-contiguous active layer zones 407 in a poly layer of thesemiconductor substrate (not shown for illustrative convenience). Thedummy structures 405 are formed in four distinct dummy fields, eachdistinct dummy field being aligned adjacent to a different corner of theoverlay mark protection zone 403. Thereafter, the poly layer isplanarized by CMP.

The embodiments of the present disclosure can achieve several technicaleffects including minimizing gate height variation of a poly layer afterCMP, reducing overlay metrology noise, and enabling accurate overlaydata feedback to a scanner for correction. Embodiments of the presentdisclosure enjoy utility in various industrial applications as, forexample, microprocessors, smart phones, mobile phones, cellularhandsets, set-top boxes, DVD recorders and players, automotivenavigation, printers and peripherals, networking and telecom equipment,gaming systems, and digital cameras. The present disclosure enjoysindustrial applicability in various types of semiconductor alignmentprocesses for 20 nm technology nodes and beyond.

In the preceding description, the present disclosure is described withreference to specifically exemplary embodiments thereof. It will,however, be evident that various modifications and changes may be madethereto without departing from the broader spirit and scope of thepresent disclosure, as set forth in the claims. The specification anddrawings are, accordingly, to be regarded as illustrative and not asrestrictive. It is understood that the present disclosure is capable ofusing various other combinations and embodiments and is capable of anychanges or modifications within the scope of the inventive concept asexpressed herein.

What is claimed is:
 1. A method comprising: determining a size and ashape of an overlay mark; determining a size and a shape of an overlaymark protection zone based on the shape of the overlay mark; determininga shape of a plurality of dummy structures based on the shape of theoverlay mark, wherein one of the plurality of dummy structures isaligned at each corner of the overlay mark protection zone; determininga size and a shape of at least one active layer zone based on the sizeand the shape of the overlay mark and the plurality of dummy structures;forming the at least one active layer zone in an active layer of asemiconductor substrate; forming the overlay mark and the plurality ofdummy structures over the at least one active layer zone in apolysilicon (poly) layer of the semiconductor substrate; and planarizingthe poly layer.
 2. The method according to claim 1, comprising: formingthe plurality of dummy structures in four distinct dummy fields; andforming the overlay mark protection zone in a square or rectangle shape.3. The method according to claim 1, comprising: forming the overlay markin a square or a rectangle shape; forming the overlay mark protectionzone in a square or a rectangle shape, respectively, with a widthoutside of the overlay mark greater than zero; and forming the pluralityof dummy structures in four distinct dummy fields each having a squareor a rectangle shape, respectively.
 4. The method according to claim 1,comprising: forming the overlay mark in a cross shape; and forming theoverlay mark protection zone in a square or a rectangle equal to orlarger than a smallest square that can be formed around the overlaymark.
 5. The method according to claim 4, comprising: forming theplurality of dummy structures in four distinct dummy fields; and formingeach of the four distinct dummy fields in a square, a rectangle, or aright angle shape.
 6. The method according to claim 5, comprising:forming the at least one active layer zone in a cross shape; and formingeach of the four distinct dummy fields in the right angle shape.
 7. Themethod according to claim 5, comprising: forming the at least one activelayer zone in a square or rectangle shape; and forming each of the fourdistinct dummy fields in the square or the rectangle shape,respectively.
 8. The method according to claim 1, comprising: formingthe at least one active layer zone as five non-contiguous regions basedon the size, the shape, and respective locations of the overlay mark andthe plurality of dummy structures.
 9. The method according to claim 1,comprising: planarizing the poly layer by chemical mechanical polishing(CMP).
 10. A method comprising: determining a size and a shape of anoverlay mark; determining a size and a shape of an overlay markprotection zone around the overlay mark based on the shape of theoverlay mark; determining a shape of a plurality of dummy structuresbased on the shape of the overlay mark; determining a size, a shape anda location of at least one active layer zone based on the size, theshape and a location of the overlay mark and the plurality of dummystructures; forming the at least one active layer zone in an activelayer of a semiconductor substrate; forming the overlay mark over the atleast one active layer zone in a polysilicon (poly) layer of thesemiconductor substrate; forming the plurality of dummy structures,wherein one of the dummy structures is formed at each corner of theoverlay mark protection zone; and planarizing the poly layer by chemicalmechanical polishing (CMP).
 11. The method according to claim 10,comprising: forming the overlay mark in a square or a rectangle shape;forming the overlay mark protection zone in a square or a rectangleshape, respectively, with a width outside of the overlay mark greaterthan zero; and forming each of the four distinct dummy fields in asquare or a rectangle shape, respectively, diagonally aligned with adifferent corner of the overlay mark protection zone.
 12. The methodaccording to claim 10, comprising: forming the overlay mark in a crossshape; and forming the overlay mark protection zone in a square or arectangle shape equal to or greater than a smallest square that can beformed around the overlay mark; and forming the active layer zone in asquare or rectangle shape and forming each of the four distinct dummyfields in a square or a rectangle shape, respectively, diagonallyaligned with a different corner of the overlay mark protection zone, orforming the active layer zone in a cross shape and forming the overlayprotection zone in a square and each of the four distinct dummy fieldsin a right-angle shape at a different corner of the overlay markprotection zone.
 13. The method according to claim 10, furthercomprising: forming the least one active layer zone as fivenon-contiguous regions.